1. Field
Example embodiments relate to an engine system utilizing a hydraulic pressure. More particularly, example embodiments relate to an engine system using a hydraulic energy in a hydraulic system of an excavator.
2. Description of the Related Art
Generally, an air conditioner for temperature control may be mounted in a cabin of construction machinery in which an engine is installed as a power source. A compressor of the air conditioner may be coupled to a crankshaft of the engine by a belt to be directly driven by the engine.
Accordingly, if the air conditioner operates during vehicle operation, an additional fuel may be consumed for a substantially same output power, thereby deteriorating fuel efficiency and the output power may be reduced while a substantially same amount of fuel is consumed. Further, in development stage of construction machinery, additional processes for tuning and control logic design required for the operation of the air conditioner may be required, thereby increasing development times and costs.
Additionally, auxiliary equipments such as a cooling water pump, a fuel pump, a fuel cooling fan, etc, which assist an operation of the engine, may be directly driven by the engine. Accordingly, fuel efficiency or output power may be reduced when the auxiliary equipments operate.
Further, in order to satisfy exhaust gas emission regulations, an EGR (exhaust gas recirculation) system may be provided in the engine system of the construction machinery. In applications of the EGR system, it may be important to design a simple, durable and controllable EGR valve.
On the other hand, recently, waste energy recovery techniques, which utilize waste energy in an exhaust gas or an engine cooling water to regenerate into electric energy or mechanical energy, have been developed actively.